It follows from Eq. (REF ) that the singlet gap function always transforms under the point group as a complex scalar, regardless of the band symmetry, therefore the usual
classification of the singlet superconducting states[1]}, [2]} is applicable. In contrast, the transformation properties of the triplet gap function essentially depend
on the band symmetry at the \(\Gamma \)  point. In a pseudospin band, we have \(\hat{\cal R}_n(g)=\hat{R}\)  and \( {d} _n( {k} )\)  transforms under \(g\)  into \(R {d} _n(g^{-1} {k} )\) , i.e., like a pseudovector.
However, this is not the case in general: if the \(\Gamma \) -point corep is such that \(\hat{\cal R}_n(g)\ne \hat{R}\) , which happens in the exceptional bands in trigonal and hexagonal crystals,
see Eq. (REF ), then \( {d} _n( {k} )\)  does not transform under \(g\)  like a pseudovector, with profound consequences for its momentum dependence and the nodal structure.[3]}
